Manage your subscription

Piecing together how the brain works

In an effort to disentangle the roles that different regions of the
brain play in complex problem solving, researchers have traced the networks
of neurons activated in chess players’ brains as they contemplate their
next move. The team, from the US government’s National Institute of Neurological
Disorders and Stroke in Bethesda, Maryland, used positron emission tomography
(PET) to observe the pattern of brain activity peculiar to playing chess.

PET scans measure the flow of blood in the brain. When an area is activated,
the flow increases, so a scan can show which areas are involved in specific
thought processes and actions.

A team led by psychologist Jordan Grafman and neurologist Paolo Nichelli
found that the overall strategy the brain uses for chess can be broken down
into simpler functions and mapped to specific areas. These functions include
memory, the ability to conjure up mental images, and planning. ‘Even though
we would call playing chess a higher-order cognitive process, it is made
up of lower-order functions,’ says Grafman.

The researchers put 10 male volunteers, all of them competitive chess
players, in front of computerised chessboards. They first asked the players
a series of questions associated with basic chess-playing skills, such as
determining the colour of chess pieces, the positions of the pieces and
the rules for moving each piece, and performed PET scans in each case.

Advertisement

The players were then shown chess positions and asked whether or not
one player could reach checkmate in a certain number of moves. The PET scan
images relating to colour, position and rules were then digitally subtracted
from the images taken during the questions about the checkmate. This enabled
the scientists to determine exactly which areas – besides those used for
the ‘simple’ tasks – are involved in planning the endgame strategy.

In this week’s Nature, they show that a large part of the posterior
cortex at the occipito-parietal junction and two parts of the prefrontal
cortex came into play. Researchers know that the posterior cortex is associated
with mental imagery, but Grafman was surprised by the size of the activated
area. ‘My interpretation is that they were rapidly scanning through the
moves in their mind,’ he says.

Grafman believes that the networks in the prefrontal cortex are used
for the planning and sequential execution of the moves needed to reach checkmate.
The functions of the prefrontal cortex are still little understood, because
people who have an injury to this part of the brain do not display obvious
mental deficits. Scientists believe this area is a sort of information manager
that organises working memory – the data that need to be kept active for
only a short time until a response is required.

Grafman and his colleagues are now trying to tease out the networks
of neurons activated by other complex tasks involving the prefrontal cortex,
including how a person deduces the moral of a story.